A dipole magnetic field topology showing gas densities in a black hole accretion disk. Dark blue indicates low gas density and dark red indicates high gas density. White lines show the magnetic field structure. Accretion disks around black holes power some of the most energetic phenomena observed in the universe. Researchers from the University of Virginia used TeraGrid resources to simulate the accretion disks. Credit: John F. Hawley, Kris Beckwith, University of Virginia; Julian H. Krolik, Johns Hopkins University